A conventional can body maker apparatus is disclosed in U.S. Pat. No. 3,696,657, issued to J. H. Maytag and an improvement to the ram assembly of the can body maker ram assembly is disclosed in U.S. Pat. No. 4,934,167, issued to C. M. Grims, et al. Both of these patents are assigned to Adolph Coors Company. The aforedescribed patents are incorporated herein by reference as if fully set forth. The assignee of the instant invention is also the assignee of U.S. Pat. No. 5,335,532, "Improved Body Maker Apparatus," which discloses a counterbalance mass system that facilitates improved speeds and operational efficiencies in can body makers.
Can body makers produce elongated can bodies from shallow metal cups or can shells. The can shells have a wall thickness of approximately 0.009 to 0.012 inch, and the elongated can bodies have a wall thickness reduced to approximately 0.0045 inch. In a conventional can body maker apparatus, a ram is movably mounted for reciprocal, straight line motion at rates sufficient to form from between 180 and 220 can bodies per minute. The ram can be supported for straight line, or X-axis, motion by a mounting structure that incorporates fluid bearing technology. However, because the ram is motivated by the circular motion of a crank assembly, minor elements of both Y-axis and Z-axis motion may be present in the reciprocal motion of the ram. The stroke length, that is the distance traveled by the movable ram, is between about 18 to 26 inches. As a general rule, for a given can body maker, the shorter the ram stroke, the greater the rate or number of cycles per minute at which the ram can be operated. Misalignment as small as between about 0.0005 and 0.0010 inch can result in the formation of defective cans. As can be appreciated, it is an ongoing objective of the can body maker industry to enhance the operation of the ram by minimizing as much as possible, any transient Y or Z axis motion in the ram.
In conjunction with the reciprocal motion of the ram, a redraw sleeve is supported in a redraw assembly. The redraw sleeve engages the shell prior to contact by the ram, applying a restraining force against the shell as the ram works the shell through a redraw die. The redraw process elongates the side walls of the can shell and decreases the side wall thickness and overall diameter of the can shell. The redraw operation is followed by two or three ironing stations that further elongate and thin the walls of the can shell to form a one piece can body. Finally, the body maker can be equipped with a doming station that further forms the enclosed bottom of the can body into a desired structural configuration. Typically, mechanical linkage is provided between the main crank shaft of the can body maker and both the ram assembly and the redraw assembly.